91 Dynasty

Car has been running fine. Now turns over but wont start. Diagnostic shows code 42 for open/short in auto shutdown relay. What is it, where is it, and why has this code popped up?

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Tuesday, March 22nd, 2011 AT 1:00 AM

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RASMATAZ

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Could be the ASD relay but do below 1st to determine if its fuel or spark problem

Get a helper disconnect a sparkplug wire or 2 and ground it to the engine atleast 3/16 away from ground-have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel related problem, Do you hear the fuel pump come On when you turn key on? If not check fuel pump fuse and fuel pump relay if okay-check the fuel pressure to rule out the fuel filter/fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil packs, coil's resistances, cap and rotor, distributor pick-up coil, ignition control module, cam and crank sensors and computer Note: If it doesn't apply disregard it and keep testing

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Tuesday, March 22nd, 2011 AT 1:03 AM

CARADIODOC

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That means when the Engine Computer turns on the automatic shutdown relay, it expects to see 12 volts on pin 57 as proof that relay turned on. It is seeing 0 volts instead meaning either the relay didn't turn on, it has pitted contacts, or something is shorted on that circuit. If something is shorted, the 30 amp fuel pump fuse under the hood will be blown. (I only have a '92 service manual which might be different). You can also try swapping the automatic shutdown (ASD) relay with another one like it but they really don't fail very often. A good place to start is by measuring the voltage on the wire feeding the ignition coil, or any injector. In '92 that was a dark green / orange wire. On the '90 models that was a dark green / black wire. You can also use either small wire on the back of the alternator. You can use a test light or an inexpensive digital voltmeter. You'll have to prop it up so you can see it from inside the car or you'll need a helper to turn the ignition switch while you watch under the hood. You must see full battery voltage on that wire for one second after turning on the ignition switch, then it will go back to 0 volts. You might hear the fuel pump run for the same one second. Under the hood you MIGHT hear the hiss from the fuel pressure regulator and the click of the ASD relay. Some digital voltmeters don't respond fast enough to catch that voltage for just one second so a test light often works better. That voltage must come back during engine cranking. Whether that voltage is there for one second and during cranking will determine where to go next.